PNNL

Abstract

The maturation of the ethanol industry has led to more readily available pathways toward renewable fuels. However, the presence of the “blendwall” problem, as well as the shift in focus toward heavier fuels, has resulted in a need for processes that can use ethanol as a building block for more valuable fuels and chemical products. Concurrently, numerous processes are being developed for the conversion of ethanol into a wide range of value-added products. One such process, the Guerbet reaction, is a well-known chemistry for coupling alcohols that has resurfaced as a promising pathway toward producing 1-butanol and other valuable higher alcohols. Though the general chemistry for Guerbet coupling is largely agreed upon, recent research interest has been focusing on developing catalysts that can achieve both high selectivities and yield. This work focused on hydrotalcite based catalysts, which are layered double hydroxide (LDH) formed by co-precipitation of divalent and trivalent metals in solution and then calcined to form the integrated mixed oxide structure. Changing the ratio of +2/+3 metals is a facile method for tuning the acid-base nature of the catalyst, and these metals can be further substituted to form ternary or quandary structures with additional characteristics. This flexible synthesis allows for the design of catalysts that have the strong-base, weak-acid sites shown to be beneficial to ethanol C-C coupling reaction to produce butanol and higher alcohol.